This disclosure relates to electrochemical cells, and, more particularly, to an apparatus in which a membrane support member is integrally formed with a frame assembly.
Electrochemical cells are energy conversion devices that are usually classified as either electrolysis cells or fuel cells. Proton exchange membrane electrolysis cells can function as hydrogen generators by electrolytically decomposing water to produce hydrogen and oxygen gases. Referring to FIG. 1, an anode feed electrolysis cell of the related art is shown at 10 and is hereinafter referred to as “cell 10.” Reactant water 12 is fed to cell 10 at an oxygen electrode (e.g., an anode) 14 where a chemical reaction occurs to form oxygen gas 16, electrons, and hydrogen ions (protons). The chemical reaction is facilitated by the positive terminal of a power source 18 connected to anode 14 and a negative terminal of power source 18 connected to a hydrogen electrode (e.g., a cathode) 20. Oxygen gas 16 and a first portion 22 of the water are discharged from cell 10, while the protons and a second portion 24 of the water migrate across a proton exchange membrane 26 to cathode 20. At cathode 20, hydrogen gas 28 is formed and is removed for use as a fuel. Second portion 24 of water, which is entrained with hydrogen gas, is also removed from cathode 20.
Another type of water electrolysis cell that utilizes the same configuration as is shown in FIG. 1 is a cathode feed cell. In the cathode feed cell, process water is fed on the side of the hydrogen electrode. A portion of the water migrates from the cathode across the membrane to the anode. A power source connected across the anode and the cathode facilitates a chemical reaction that generates hydrogen ions and oxygen gas. Excess process water exits the cell at the cathode side without passing through the membrane.
A typical fuel cell also utilizes the same general configuration as is shown in FIG. 1. Hydrogen gas is introduced to the hydrogen electrode (the anode in the fuel cell), while oxygen, or an oxygen-containing gas such as air, is introduced to the oxygen electrode (the cathode in the fuel cell). The hydrogen gas for fuel cell operation can originate from a pure hydrogen source, a hydrocarbon, methanol, an electrolysis cell, or other source that supplies hydrogen at a purity level suitable for fuel cell operation. Hydrogen gas electrochemically reacts at the anode to produce protons and electrons, the electrons flow from the anode through an electrically connected external load, and the protons migrate through the membrane to the cathode. At the cathode, the protons and electrons react with oxygen to form water.
Conventional electrochemical cell systems generally include one or more individual cells arranged in a stack, with the working fluids directed through the cells via input and output conduits formed within the stack structure. The cells within the stack are sequentially arranged, each including a membrane electrode assembly (hereinafter “MEA”) defined by a cathode, a proton exchange membrane, and an anode. Each cell typically further comprises a first flow field in fluid communication with the cathode and a second flow field in fluid communication with the anode. The MEA may be supported on either one side or both sides by flow field support members such as screen packs or bipolar plates disposed within the flow fields, and which may be configured to facilitate membrane hydration and/or fluid movement to and from the MEA.
Each cell of the cell system and its supporting structure is held in place by frames. A protector ring is typically positioned adjacent to the gap defined by the juncture of the inside perimeter of the opening of the frame and the flow field support member. Because the surface of the protector ring that covers the gap is only slightly larger than the gap itself, positioning of the protector ring over the gap oftentimes results in “pinching” of the protector ring between the frame and the flow field during the assembly of the cell system or its operation. Such pinching may cause a misalignment of the protector ring over the gap, thereby resulting in a less than optimum performance of the cell system in general.
Furthermore, resistance to the electrical communication may result from the misalignment of the protector rings, thereby affecting the performance of the electrochemical cell. In particular, the power production of fuel cells and the power consumption of electrolysis cells may be adversely affected by increases in electrical resistance caused by discontinuities between the MEA and flow fields. Such discontinuities may be caused by damage of the MEA resulting from the pinching of the MEA in the gap between the frame and the flow field.
While existing frames and protector rings may be suitable for their intended purposes, there remains a need for improvements, particularly regarding the prevention of misalignment of the protector rings relative to the gaps between the cell frames and the flow field support members. Such a need may be addressed by the integration of a frame with its associated cell components to eliminate the gap between the frame and the cell structure, thereby allowing optimum performance of the electrolysis cell to be realized.